Melt-processed polymer glasses for low-power upconversion via sensitized triplet–triplet annihilation

Glassy poly(methacrylate) terpolymers with covalently attached emitters and sensitizers for low-power light upconversion

“…Very much like the normal fluorescence caused upon direct excitation of the DPA motifs ( vide supra ) the upconverted fluorescence intensity decreased with increasing PdmPH3P content. This trend was already observed in previously studied PMMA blends, as well as in copolymer blends . The data shown here suggest that exciplex formation appears to be the culprit.…”

“…For instance, in the case of polymer‐tethered emitters, the maximum upconversion intensity increased with the emitter content up to a DPA content of about 35 wt %, but dropped markedly when the DPA content was further increased. In addition, all glassy materials with high DPA content studied by us thus far, display a decreasing UC emission intensity with increasing porphyrin content . Several hypotheses have been put forth to explain this behavior, including limited triplet diffusion, reabsorption, excimer formation and porphyrin aggregation, which was spectroscopically confirmed in the case of Pt octaethyl porphyrin compounds …”

“…We subsequently reported the incorporation of the PdOEP‐DPA UC chromophore pair into an amorphous poly(methyl methacrylate) (PMMA) matrix by melt‐processing. This strategy permitted to considerably increase the DPA content by kinetically trapping up to 20 wt % of the sensitizer using rapid cooling of homogeneous melts . To further increase the emitter content, two avenues were explored by our group, the use of a molecular‐glass‐forming DPA derivatives and the covalent tethering of DPA derivatives to polymers .…”

Single-Component Upconverting Polymeric Nanoparticles

“…Covalent attachment of the UC dyes to a poly(methyl methacrylate) (PMMA) backbone was recently proposed as strategy to avoid phase segregation of palladium octaethylporphyrin (PdOEP) and diphenylanthracene (DPA) even at high concentration into glassy materials . It has been shown that polymeric solid‐state materials allow for good dispersion of the sensitizer and the emitter controlling precisely their concentration to tune UC properties . Capitalizing on these findings, we explored the possibility to create nanoparticles from a methacrylic terpolymer bearing pendant DPA emitter and meso‐phenoxytris(heptyl)porphyrin‐ethylmethacrylate (PdmPH3PMA) sensitizer groups.…”

“…The annihilation of two emitter triplet excited states eventually produces a singled excited state, which (if relaxation occurs radiatively) leads to the emission of one photon of higher energy. [ 1,3 ] Initially studied in solution, [ 4,5 ] TTA-UC dye pairs were recently introduced into polymer systems, e.g., in rubbery polymers, [ 6,7 ] polymer glasses, [8][9][10] and organogels. [ 11 ] Concomitantly, the preparation of upconverting nanoobjects based on TTA-UC has undergone a rapid development in the past fi ve years.…”